1. Field of the Invention
The present invention relates to a radiation exposure test and, more particularly, to a system and a method for a radiation exposure self-test (REST) that provides a near real-time, rapid and accurate indication of radiation exposure.
2. Description of Related Prior Art
A significant amount of funding has been spent in the development of medical and nonmedical countermeasures that are directed at counteracting the consequences of an intentional attack/accident by an improvised nuclear/radioactive device. As is well known in the art, when a victim/patient is exposed to ionizing radiation, such as that emitted as a result of the intentional/accidental detonation of a nuclear/radiological device, it is highly advantageous to administer medical countermeasures and/or medical treatment as close to the time of exposure as possible. That is, it is generally acceptable and advisable to administer such medical countermeasures and/or medical treatment to counteract exposure to radiation within 24 hours so as to increase the probability that such medical countermeasures and/or medical treatment will decrease morbidity and mortality of potential patients. Personal dosimetry is of particular importance as a supplement to or replacement to direct in-vivo or direct physiological indicators or biomarkers. At present time current technology measures delayed manifestations such as chromosomal aberrations and white blood cell counts. In fact, some victims who will eventually die from ARI in the hours and days after exposure may be asymptomatic and without significant physical complaints in the first few days after exposure, thereby missing the time frame when medical counter measures (MCM) would be most effective.
It is contemplated that detonation of an improvised nuclear device, within an urban area, could easily impact over 1 million potential patients as cited in the DHS planning scenarios. It is to be appreciated that up to ten or more times that number of victims may actually show up for testing. Such detonation would result in immediate deaths due to traumatic injuries, burns and acute radiation illness, and additional deaths due to prolonged evacuation, loss of continuity of current medical care and limited access to personal protective information and supplies. Widespread destruction could lead to panic and civil unrest. Radioactive contamination and continued exposure, through ingestion and inhalation of radioactive particles, would present ongoing medical and environmental issues. There also could be a significant loss of critical infrastructure such as command and control, hospital and resource buildings, communications, power, and water due to immediate destruction, contamination and electromagnetic pulse damage, thereby limiting, or severely hindering at the very least, the ability of the local, state and federal authorities to provide the necessary care for the potential patients in need of life-saving medical intervention and/or treatment.
It is further recognized that popular and urgent national research objectives to obtain in-vivo measurements in fingernails and teeth are fundamentally and significantly flawed. For example, in terms of obtaining accurate and timely measurements in the in-vivo environment and the sub-optimal nature of the matrices, it is highly unlikely that these systems will be utilized effectively in a true mass casualty incident, and the measurements obtained are not a direct measurement of physiological response, rather a measurement of sub-atomic changes occurring within inert materials within the body. This effort may be causing delays in the development of a system that would potentially save countless lives in the event that a nuclear mass casualty incident were to occur.
A significant amount of the current effort underway is focused on developing technologies that take in-vivo measurements from either a tooth or fingernails. In-vivo versus in-vitro testing is usually done to determine the clinical impact on a living organism bases on the actual response of the body or tissue, for example. In the case of in-vivo measurement of teeth or fingernail(s), there is no direct indication of clinical response of the body that could not be obtained from an optimized personal dosimeter such as a driver's license, a credit card or some other measurable material carried in close proximity to the body of an individual. This distinction, by itself, could save significant funding in the final costs of implementing, development, building, deploying and eventual FDA approval thereby leading into a new area of measurement that would be more cost effective, faster, portable and provide the same information. A desired system will quickly identify potential patients in a non-invasive manner in a much shorter period of time.
In public health, the term “herd immunity” is used to describe a large enough group that has become immune—usually through vaccination—so that the few members that are not vaccinated have an extremely unlikely chance that they will ever come in contact with an infected member, therefore, halting the spread of an infectious disease. With radiation exposure, the term “herd exposure” could be utilized. In this case, by measuring enough potential patients within a certain geographical area, via a rapid self-test procedure, then at some point, a determination could be made that within this group, testing can be discontinued with confidence that no immediate medical care needs to be given or, at the other extreme, that more medical resources are required to be moved to a specific area based on the number of positive tests.
During the time of such a nuclear detonation or any other similar mass casualty public health event or disaster, it is believed that there will be a significant need to accurately identify, screen, triage, and gather data from thousands, if not hundreds of thousands, or millions of potential patients over a very short period of time, optimally 24 hours. Further, there may also be a need to identify, screen, then triage the entire population of citizens residing within a certain radius (e.g., a 2 mile radius, a 5 mile radius, a 10 mile radius, a 20 mile radius, etc., depending upon the size of the nuclear detonation and environmental conditions) of ground zero of the nuclear detonation in order to determine which potential patients require immediate medical attention and which potential patients, due to either limited, minimal or possibly no exposure to the radiation, may defer medical attention or receive the necessary support or preventative treatment within a few days or possibly a few weeks, for example, or may not require any medical countermeasures, medical treatment or any attention at all. Moreover, given that the population that may be affected by such a mass disaster could conceivably amount to 1 million or more potential patients, the current medical screening and triage processes are generally unacceptable and insufficient to handle such a large volume of potential patients within such a short duration of time, e.g., within 24 or 48 hours, for example, of the nuclear detonation or some other mass casualty event or public health or disaster.
A mean lethal dose of radiation, which typically kills 50% of human beings within sixty (60) days, is a whole-body radiation dose of typically between 3.25 to 4 Gy when, following exposure to such radiation, the victim/patient does not receive any medical care or treatment. However, if the victim/patient receives medical care and attention, such as myeloid cytokines, G_CSF, Filgrastim, supportive care, antibiotics, anti-nausea medicines, bone marrow transplants, for example, following whole body exposure to radiation of a dose greater than about 2-3 Gy, then the patient has a higher probability of surviving such radiation exposure. The ability to rapidly self test individual patients within a very short period of time, i.e., 15-30 seconds per test per person (total test time is variable and would include sample scan time, card insertion and release time, patient movement through kiosk), would allow near real time allocation and distribution of resources to the patients most requiring life saving or supportive care. Further, depending on available resources, it is generally accepted that a whole-body dose of radiation of greater than 8-10 Gy is likely to be lethal to any victim/patient in a mass casualty setting.
Researchers are currently developing and testing equipment to measure dose levels in the tooth enamel and fingernails of potential patients of a radiological or a nuclear catastrophe, including a terrorist attack. At present, such test equipment is relatively large, bulky, sensitive to vibrations and temperature, difficult to operate, subject to in-vivo variations, and victim/patient movement. Each measuring device must be operated by specifically trained personnel, and typically requires a scan or data acquisition time of over 5-10 minutes. In addition, the additional time associated with removing the previous victim/patient, fitting new victim/patient, removing and putting on a new pair of gloves, gathering and adding disposables, readjusting tooth or fingernail placement, taking additional universal precautions against infectious disease and allowing additional time for patient movement and re-test if the patient moves significantly during the test procedure, could bring the total cycle time for each patient to typically between at least 10-15 minutes. Many times the patient must be rescanned in order to obtain more accurate data and assess confounding factors such as discolorations, moisture content, recent fingernail clipping and co-existing illness, for example. Infant or younger pediatric patients who may also be preferentially exposed, would typically be unable to remain still for such long scan times or may not have sufficiently developed teeth (for example, deciduous teeth may be too small for an accurate measurement). Likewise, elderly patients or those with significant prior dental work may not be eligible for this test and are less likely to accurately describe symptoms. Lastly, the associated test equipment is fairly expensive, with an estimated cost of several hundred thousand dollars, and, as noted above, is delicate, large and requires specially trained personnel to operate.
Even if the current in-vivo fingernail or tooth test equipment were operationally viable, and logistically considerations such as high replacement and storage costs were appropriately addressed, the difficulty of moving delicate and bulky equipment, expendables, such as magnetic coils, plastic coverings, OSHA protections, gloves, gowns, masks, and other supplies, become very expensive and time consuming. Aside from the mentioned concerns, current in-vivo fingernail or tooth dosimetry still has limited capability for assisting in the screening and triage of many hundreds of thousands or millions of victims/patients in a clinically meaningful time frame. Such equipment can only test approximately 4 patients per hour that translates to about 48 patients per day and 96 patients over the course of two days. This time frame is too long, and would limit the number of patients able to receive care within the time when it is highly recommended for medical treatment for radiation exposure. Further illness and death would result from delays in decontamination, evacuation and supportive care and loss of continuity of current medical conditions. Accordingly, such test equipment is unacceptable for assisting with the screening and triaging of many hundreds of thousands of potential patients who would likely be seeking testing after a large-scale radiological event.
Generally speaking, there is a concern relating to two types of exposure: acute and chronic. An acute exposure is a single accidental exposure to a high dose of ionizing radiation over a short period of time directly resulting in acute radiation illness when exposure is high enough. An acute exposure has the potential for producing both non-stochastic and stochastic effects. Chronic exposure, which is also sometimes called “continuous exposure,” is long-term, likely low level overexposure. Chronic exposure may result in stochastic health effects and is likely to be the result of improper or inadequate protective measures, prolonged exposure with direct inhalation and ingestion of a variety of radioactive particles. As is well known in the art, there are three basic ways of controlling exposure to harmful radiation, namely, 1) limiting the time spent near a source of radiation, 2) increasing the distance away from the source, 3) and using shielding to stop or reduce the level of radiation. In addition, the radiation dose is directly proportional to the time exposed to the radiation. Therefore, a victim/patient should not stay at or near a source of radiation any longer than is absolutely necessary. Some mitigating activities could include appropriate personal protective actions, precise, regular and consistent public messaging, sheltering in place, rapid decontamination and evacuation. By utilizing a radiation exposure self-test in a significant radiological or nuclear event, patients will be rapidly triaged and screened and monitored over time with repeated testing, therefore allowing reassurance and efficient mitigating and personal protective actions to occur. The following equation can be used to make a simple calculation to determine the dose that will be or has been received in a radiation area.Dose=Dose Rate×Time.
It is to be appreciated that increasing distance from the source of radiation will reduce the dose of ionizing radiation received by a victim/patient. That is, as the radiation travels from the source, the radiation spreads out and becomes less intense. This phenomenon can be expressed by an equation known as the inverse square law, which states that as the radiation travels out from the source, the dosage decreases inversely with the square of the distance.Inverse Square Law: I1/I2=D22/D12 
As noted above, shielding is a way to reduce exposure to radiation. Generally, the denser the shielding material is, the greater the protection that will be provided by the shielding material. For example, depleted uranium and other heavy metals, like tungsten, are very effective in shielding radiation because their tightly packed atoms make it difficult for radiation to travel through the material without interacting with the atoms. Lead and concrete are the most commonly used radiation-shielding materials primarily because they are easy to work with and are readily available materials. Concrete is commonly used in the construction of radiation vaults.
As evident above, a continuing need exists for a radiation exposure self-test that will provide a near real-time, rapid and accurate indication of radiation exposure.